(1) Field of the Invention
The present invention relates to a semiconductor supporting device for supporting or chucking a semiconductor material such as a semiconductor wafer.
(2) Related Art Statement
An electrostatic chuck is used for chucking and holding a semiconductor wafer in subjecting a semiconductor wafer to transferring, light exposure, film forming such as CVD or sputtering, fine working, cleaning, etching or dicing. Dense ceramics have been noted for substrates for such an electrostatic chuck. Particularly in the semiconductor producing apparatus, a halogen-based corrosive gas such as ClF.sub.3 is frequently used as an etching gas or a cleaning gas. Dense aluminum nitride has high corrosion resistance against the above halogen-based corrosive gas. It is known that aluminum nitride is a highly thermal conductive material, and has high thermal shock resistance. Therefore, it is considered that a substrate for the electrostatic chuck of the semiconductor-producing apparatus is favorably made of an aluminum nitride-based ceramic material.
In Japanese patent application No. 4-58727 (filed on Feb. 13, 1992), NGK Insulators, Ltd. disclosed that an aluminum nitride sintered body having a layer of aluminum fluoride on its surface has high corrosion resistance against a plasma of the above halogen-based corrosive gas. That is, even when the aluminum nitride sintered body was exposed to, for example, ClF.sub.3 for one hour, its surface state, no change was observed on its surface.
NGK Insulators, Ltd. disclosed that a film of aluminum fluoride is formed on a surface of an aluminum nitride sintered body by a gas phase process such as a CVD process (Japanese patent application Laid-open No. 5-251365). Japanese patent application Laid-open No. 7-273053 discloses that in order to prevent corrosion of the surface of an electrostatic chuck for a semiconductor wafer, the surface of the electrostatic chuck is treated to preliminarily making replacement with fluorine and produce AlF.sub.3 at the surface of the electrostatic chuck.
During the course of investigating aluminum nitride as a material for the semiconductor wafer-supporting susceptor such as the electrostatic chuck, the present inventors tackled a study to improve corrosion resistance at a surface region of the susceptor against the halogen-based corrosive gas by changing and controlling anisotoropy of aluminum nitride constituting the susceptor. This study is based on the recognition that particles which would cause a defect of the semiconductor may be generated by fine corrosion of the surface of the susceptor as not having been considered as a problem, with the semiconductor producing process being made finer, and consequently the corroding speed at the surface region of the susceptor is equired to be further decreased.